Application having trouble when opening with network - objective-c

Question

I'm building an app that is using the Instagram API to display photos but I'm running into some trouble. The app is crashing when there is no network connection and I have found the code that is causing the problem.
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
self.accessToken = [userDefaults objectForKey:#"accessToken"];
if (self.accessToken == nil) {
[SimpleAuth authorize:#"instagram" options:#{#"scope": #[#"likes"]} completion:^(NSDictionary *responseObject, NSError *error) {
self.accessToken = responseObject[#"credentials"][#"token"];
[userDefaults setObject:self.accessToken forKey:#"accessToken"];
[userDefaults synchronize];
[self refresh];
}];
} else {
[self refresh];
}
I have found that the [self refresh]; is causing the problem in the else block and I tried to replace it with a alert view like this
UIAlertView *networkError = [[UIAlertView alloc] initWithTitle:#"Network Error" message:#"Please connect your device to a network and restart application" delegate:nil cancelButtonTitle:nil otherButtonTitles:nil];
[networkError show];
However, with this problem I find that if I open the app with a network connection I still get the alert. Any help would be great because I'm still new to Objective C!
Thank you for the help!

Answer 1

I know this code from Treehouse :).
The thing is that the if (self.accessToken == nil) { /.../ } block will only get execute when the app is not authorized using your Instagram credentials.
Once you logged in successfully, it will always execute the code in the else { /.../ } block. If it has connection to Internet, it will do its work, download, display images etc. If you insert the code to display alert, it will always do that because you actually mean that by that code.
If you want to check if there is some connection, you need to do that before all that code, display an error and return instantly if connection is not available. However, the author tried to keep things simple, assuming there is always Internet connection.
Hope it makes you understand it.
This is the some code you can use for checking if there is connection:
// show some activity indicator
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
// Do something...
[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
NSURL *url = [NSURL URLWithString:#"http://www.apple.com/"];
NSString *s = [NSString stringWithContentsOfURL:url
encoding:NSUTF8StringEncoding
error:nil];
dispatch_async(dispatch_get_main_queue(), ^{
// hide the activity indicator
self.connected = (s != nil);
[[UIApplication sharedApplication] endIgnoringInteractionEvents];
if (self.isConnected)
{
NSLog(#"self.connected == YES");
}
else
{
NSLog(#"self.connected == NO");
NSString *alertMessage = #"In order to load images, you need an active Internet connection. Please try again later!";
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Sorry!"
message:alertMessage
delegate:nil
cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[alert show];
}
});
});
You obviously need to add a property to you class. You can insert this code:
#interface LDPhotosViewController ()
#property (nonatomic, copy, getter = isConnected) NSString *connected;
#end
at the top of LDPhotosViewController.m file, before the #implementation line.